The invention relates to a turboramjet engine having a ram pressure air duct shrouding the basic turbo-engine in an annular manner, this ram pressure air duct, when the ramjet operation is disconnected, while at the same time intake air is released into the basic engine, being blocked with respect to the supply of ram pressure air.
Recently, combined turboramjet engines have been regaining importance, specifically within the framework of so-called "hypersonic flight concepts" with an extremely high mission spectrum from the start to a high supersonic speed at high flying altitudes (up to an altitude of approximately 30 km). Among other concepts, the hypersonic flight concepts include a space flight equipment concept (Sanger Project) which, as will be described in the following, amounts to a two-stage concept. The first stage is to be carried by a flight apparatus which operates only within the atmosphere, while the second stage is based on a useful-load flight apparatus which is taken along in a "piggyback" manner by the mentioned flight apparatus. The useful-load flight apparatus, for use in space missions, has the purpose of continuing its assigned flight path on its own in the upper range of the atmosphere by way of a suitable rocket propulsion system. The flight apparatus responsible for the first stage must therefore be able to return, must be reusable, and carries out starts and landings like a conventional airplane.
In the case of combined turboramjet engines which are to be used, for example, for a flight apparatus of this type the turbojet engine must generally be switched off continuously, and the respective ramjet engine must be switched on continuously when a flying speed of approximately Mach 3 is reached in order to reach the desired high supersonic or hypersonic speeds of up to Mach 4.5 or even higher only by means of the latter. Flying speeds of approximately Mach 2 or even higher may be reached in this case in a combined operation of "a turbojet engine with a switched-on afterburner". The afterburner which, for this purpose, is advantageously connected behind the turbojet engine part or behind the basic turboengine and, if necessary, is acted upon by a combination of compressor air parts and engine exhaust gas, may form the driving system for the ramjet operation by means of the connection of additional fuel injection devices, in addition to flame stabilizers, with a correspondingly apportioned exclusive ram pressure supply when the turbojet engine part is disconnected.
In this case, the ram pressure air supply to a common afterburning/ramjet combustion chamber connected behind the basic turbo-engine may take place by way of a ram pressure air duct extending in parallel to or in a coaxial shroud with respect to the basic engine. This ram pressure air duct, while at the same time continuously releasing the required air flow into the basic engine, would have to be blocked or vice versa. For operational reasons, a reliable temperature resistant blocking of the basic engine must be ensured during an exclusive ramjet operation with respect to the ram pressure air duct, particularly with respect to the comparatively high temperatures of approximately up to 1,700 degrees C or even above which exist in it. This blocking relates to the air intake side but also to the exhaust gas outlet side of the basic turbo-engine with respect to the ram pressure air flow which locally flows together behind it to the afterburning/and supplementary burning device.
Concerning the blocking devices to be selected, it is particularly important in the case of such a combined engine concept that continuous "smooth" change-over load phases from the one operating method (gas turbo-engine operation/ramjet operation or ramjet operation/gas turbo-engine operation) are ensured. Specifically, this can be ensured without, as a result, having to cause engine dimensions which take up a lot of space as a result of their circumference, among other reasons, also with respect to an increased end face resistance. In order to prevent an unacceptably strong thrust decay in the critical change-over phases, a ram pressure and intake pressure supply must be still available for the ramjet propulsion system as well as for the basic turbo-engine system respectively which is still sufficient for the respective continuous switching-off.
Concerning the blocking devices to be selected in the case of an engine concept of this type, a construction is important which is not susceptible to disturbances and has relatively few moving components together with the pertaining adjusting devices. Among other things, this has the purpose of assessing the danger of a component breakage to be as low as possible in order to prevent, if possible, that fragments are taken in by the compressor of the basic engine and may thus cause considerable damage to the engine.
It is an object of the invention to provide a combined gas turbine ramjet engine by means of which the different operating methods (ramjet operation/turboengine operation) can be reliably controlled, particularly in the critical change-over phases from one operating method to the other, without any unacceptable thrust decay. In this case, particularly on the air intake side, a reliable blocking of the basic turboengine is to be achieved with respect to the ram pressure air supply released in this case.
According to the invention, this object is achieved by providing an arrangement wherein an intake side air inflow cross-section (Z) of the basic engine is unblocked or blocked with respect to the flow divider by the axial adjustment of a drop-shaped body,
wherein a ring slide is provided which is axially adjustable to always be opposing this drop-shaped body, this ring slide blocking the ram pressure air duct when the inflow cross-section (Z) of the basic engine is unblocked and unblocking it when the inflow cross-section (Z) is blocked, and
wherein the ram pressure air duct is widened in a multicornered manner in the upstream direction at the level of a blocking zone caused by the local overtravelling of countersurfaces of this drop-shaped body and the ring slide.
By using an annular ram pressure air duct which causes a relatively minor widening of the diameter of the overall engine, the different operating methods may be controlled perfectly without having to accept any significant end face widening of the overall engine which is connected with reductions in performance.
Among other things, it is also achieved that an aerodynamically perfect air intake geometry for the compressor is made available when the ramjet engine or the propulsion system is disconnected and when only the gas turbo-engine is operating.
According to the invention, it is particularly advantageous that particularly the blocking devices arranged on the air intake side (drop-shaped central body/ring slide), as the critical change-over phases, are constructed to be controlling continuously in opposing movement phases without causing any thrust decay. A significant contribution to solving this problem is the indicated local widening of the annular shroud (ramjet pipe) carrying the ram pressure air in the form of a contour ending in a multicornered manner in such a way, during a mutual overtravelling and blocking phase of both slide devices caused during the change-over operation, the ring slide has always moved so far into the spatial widening that in this phase--between the ring slide and local zones of the widening of the outer shroud--sufficiently large parts of air can flow off into the ram pressure air duct and into the basic turbo-engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.